The present invention relates to vehicles having magnetic drives for conveying a variety of tool heads over a ferromagnetic surface. A laminated magnetic wheel is particularly shown that has groups of annular magnetic pole sets that define a rolling surface and which pole sets are resiliently mounted to flex at surface irregularities and discontinuities without disrupting wheel contact.
Maintenance on a variety of structural, ferromagnetic metal surfaces, such as found in ships, storage tanks, silos and smokestacks, is normally performed after a system of scaffolds and other work supports are erected. The manual setup and maintenance operations require 1 are typically very time consuming and costly due to the involved manual labor.
Varieties of magnetic vehicles fitted with appropriate tool heads have been developed to perform these tasks. Such vehicles can reduce the man-hours. Examples of various track vehicles are shown a U.S. Pat. Nos. 3,682,265; 3,777,834; 3,960,229; 4,789,037; 4,890,567; and 5,285,601 and Japanese patent 62-12482.
The tracks of the foregoing vehicles either contain a series of electromagnets or permanent magnets that are mounted to the vehicle tracks or to the vehicle chassis. Where the magnets are mounted to the tracks, the magnets rotate with the tracks to progressively engage and disengage the work surface. A number of magnet elements are thereby always in contact with the work surface, while others are not.
Track drive assemblies, however, are costly and physically heavy. The extra weight necessitates additional holding power. The added costs limit the economic advantages. The maneuverability of track vehicles is also limited by the speed and braking controls necessary to properly steer and maneuver the separate tracks. Track drives also have difficulty in maintaining contact with work surfaces exhibiting tight surface curvatures, surface irregularities (e.g. rivets, welds or other discontinuities or disruptions) or containing rust, dirt or other surface residue or contaminants.
Wheeled magnetic vehicles are also known and examples are shown at U.S. Pat. Nos. 2,030,840; 2,694,164; 3,690,393; 3,734,565; and 5,355,807. Maintaining surface is especially important with wheels. The relatively small area of tangential contact of each wheel with the surface particularly limits the holding power of each wheel. Surface contact is also lost or restricted to a small area when discontinuities or irregularities are encountered.
The magnetic wheel of the subject invention was developed to overcome the foregoing shortcomings. The wheel provides laminated groups of annular magnetic pole sets. Each pole set supports a number of magnetic pole pieces. The pole sets are resiliently supported at each wheel to permit one or more pole sets to vertically flex upon encountering surface irregularities. An optimal number of magnetic pole sets are thereby able to maintain contact with the work surface during traversal of the surface. Independent, resilient suspensions separately support each of the wheels to the vehicle chassis to further optimize wheel contact with the surface.